FROMGIT: mm/hugetlb: fix build with !ARCH_WANT_HUGE_PMD_SHARE

want_pmd_share() is undefined with !ARCH_WANT_HUGE_PMD_SHARE since it's
put by accident into a "#ifdef ARCH_WANT_HUGE_PMD_SHARE" block.  Moving it
out won't work either since vma_shareable() is only defined within the
block.  Define it for !ARCH_WANT_HUGE_PMD_SHARE instead.

Link: https://lkml.kernel.org/r/20210310185359.88297-1-peterx@redhat.com


Fixes: 5b109cc1cdcc ("hugetlb/userfaultfd: forbid huge pmd sharing when uffd enabled")
Signed-off-by: Peter Xu <peterx@redhat.com>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

(cherry picked from commit 5038f9dd8bbde13ff16435011bb3b0981acc5c1c
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git akpm)
Link: https://lore.kernel.org/patchwork/patch/1393174/



Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
Bug: 160737021
Bug: 169683130
Change-Id: Id716afd43bff303f7eda2c4f70f18d9ea727c698